1. Field of the Invention
This invention relates to a semiconductor device of the surface-mountable type, such as chip-size packages or similar.
This invention further relates to a magnetic sensor and magnetic sensor unit for measurement of the direction of a magnetic field.
Priority is claimed on Japanese Patent Applications No. 2004-87139, filed Mar. 24, 2004, and No. 2004-87140, filed Mar. 24, 2004, the content of which is incorporated herein by reference.
2. Description of the Related Art
Recent years have seen the appearance of LSI and other semiconductor devices formed in dimensions substantially the same as those of the semiconductor chip, such as chip-size packages (hereafter called “CSPs”) and similar, and capable of surface mounting. Such technologies are attracting attention as mounting technologies suitable for smaller and lighter electronic equipment (see for example Japanese Patent Application, First Publication, No. 2002-156204).
In conventional surface-mounted semiconductor devices, a plurality of bump electrodes for electrical connection to the mounting board are arranged on the top side of the semiconductor chip, having equal widths.
That is, as shown in FIG. 12, a plurality of virtual lattice lines L21 are provided, extending in one direction (the X direction) along the surface of the semiconductor chip, so as to divide the surface of the semiconductor chip substantially equally.
Further, similarly to the above, a plurality of virtual lattice lines L22 are also provided, extending in a direction (the Y direction) along the surface and orthogonal to the X direction, so as to divide the surface of the semiconductor chip substantially equally. A plurality of bump electrodes 97 are then arranged, with one each at the intersections of these lattice lines L21, L22. Each of the bump electrodes 97 is electrically connected to a pad electrode 95 on the surface of the semiconductor chip by a wiring layer provided on the surface of the semiconductor chip.
In order to reduce the size and weight of electronic equipment, integration of semiconductor devices with functional elements is also being employed. Such semiconductor devices are provided with, for example, magnetic elements, Hall elements, piezo elements, or other sensor elements having electrical functions, arranged either together with or on the surface side of the integrated circuits on the surface of the semiconductor chip. The sensor element is placed in a prescribed position on the surface of the semiconductor chip. That is, for example in a case in which sensor elements are magnetic elements used for measurement of the direction of an external magnetic field, when the semiconductor device is mounted on a mounting board, the direction of the magnetic field to be detected by each such magnetic element must be confirmed, and the magnetic elements must be positioned at a distance from each other so as not to be affected by other elements; hence elements are arranged in the peripheral portions of the surface of the semiconductor chip or in other predetermined positions.
However, the sizes of the semiconductor chips of the above conventional semiconductor devices are themselves tending to become smaller with each passing year, so that wiring portions and bump electrodes 97 are arranged in positions which overlap with sensor elements 99 in the semiconductor chip thickness direction. In the case of such a configuration, when the semiconductor device is mounted on a mounting board, the stress of the bump electrodes 97 reaches the sensor elements 99. And in the case of such a configuration, if there is bending in the region of the mounting board on which the semiconductor device is mounted, with the semiconductor device in the mounted state on the mounting board, stress arising from the bending of the mounting board reaches the bump electrodes 97 and, via posts and wiring layers, the sensor elements 99. Moreover, when in such cases the semiconductor device is mounted or operated, heating of the semiconductor device occurs, and stress arises from thermal deformation of wiring layers at this time, so that the stress on the wiring layers also reaches the sensor elements 99.
That is, when a semiconductor device is mounted on a mounting board, or when a semiconductor device is caused to operate, the stress on the bump electrodes 97 and wiring layers reaches the sensor elements 99, and so there is the problem that the characteristics of the sensor elements 99 may fluctuate or be degraded.
Further, when sensor elements 99 may affect a magnetic field, as in the case of magnetic elements and Hall elements, if bump electrodes 97, posts and wiring layers are placed in positions overlapping with sensor elements 99, there is the problem that the characteristics of the sensor elements 99 may fluctuate due to the current-induced magnetic field arising due to current flowing in posts and wiring layers.
In the prior art, magnetic sensors are provided which detect magnetic fields for measurement of the direction in three dimensions of an external magnetic field. As this type of magnetic sensor, there are sensors in which a magnetosensitive portion (magnetic sensor chip) is affixed to the surface of a magnetosensing surface holding plate, and the magnetosensensing surface holding plate and magnetosensitive portion (magnetic sensor chip) are sealed with mold compound (see for example Japanese Patent Application, First Publication No. 2002-156204).
Here, the magnetosensitive portion is configured so as to detect magnetic components in a direction along the surface of the magnetosensing surface holding plate. The magnetosensing surface holding plate and magnetosensitive portion are covered by mold compound in a state of contact with the surface of the circuit board or other element supporting portion and inclined with respect to the horizontal base. That is, in the state in which the magnetic sensor is mounted on the element supporting portion, the plate and the magnetosensitive portion are inclined with respect to the surface of the element supporting portion. By providing two of the magnetic sensors on the element supporting portion, such that the directions of inclination of the two magnetosensitive portions with respect to the surface of the element supporting portion are different, the three-dimensional direction of an external magnetic field can be measured.
However, in the case of a magnetic sensor with the above configuration, the magnetosensitive portion is affixed to the surface of the magnetosensing surface holding plate using silver paste. At the time of this affixing, the silver paste must be melted, so that the magnetosensitive portion and the magnetosensing surface holding plate are heated to elevated temperatures.
However, in the case of the above magnetic sensor of the prior art, because the magnetosensing surface holding plate and the magnetosensitive portion are heated, when the magnetosensing surface holding plate and the magnetosensitive portion comprise materials with different thermal expansion coefficients, bending of the magnetosensitive portion occurs due to the difference in thermal expansion coefficients. And when bending occurs in the magnetosensitive portion, there is the problem that the characteristics of the magnetosensitive portion are degraded, and the three-dimensional direction of an external magnetic field cannot be measured accurately.
This invention was devised in light of the above-described circumstances, and has as an object the provision of a semiconductor device which can suppress fluctuations in and degradation of the characteristics of a sensor element provided on the surface of a semiconductor chip.
This invention was devised in light of the above-described circumstances, and has as a further object the provision of a magnetic sensor and magnetic sensor unit which prevent degradation of the characteristics of a magnetic sensor chip, and enable accurate measurement of the three-dimensional direction of a magnetic field.